Dual end stop actuator and method

ABSTRACT

A dual end stop is provided for setting precise open and closed positions for the valve to which the pneumatic actuator is attached. In a preferred embodiment, a stop assembly housing contains two stop adjustment bolts as well as a cam that defines first and second stop surfaces. The stop assembly housing is preferably mounted to the actuator housing outside of the pressurized zone contained by the actuator housing. The stop bolts and associated threaded apertures are designed for minimum overhang of the stop bolts to provide more support. The stop assembly housing not only preferably houses the stop assembly components but also preferably serves as an adaptor plate for the various valves to which the actuator may be mounted. The stop bolts preferably have a convex head to provide a defined point contact rather than a random point contact as may be produced with flat heads. The cam is preferably mounted between two directly adjacent bearings, at least one of which is preferably located in the stop assembly housing. The stop assembly housing is milled to fit precisely within a recess in the actuator housing for improved support and more accurate alignment as well as eliminating the need for machining more than two bolt holes for attaching the stop assembly housing to the actuator housing.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to rotary valve actuatorsand, more particularly, to apparatus and methods for a dual end stopactuator adjustment.

[0003] 2. Description of the Backgound

[0004] Actuators, such as a piston activated pneumatic actuators, arewell known in the prior art for controlling valves between an openposition and a closed position. An exemplary and highly compactconfiguration for a pneumatic actuator is shown in U.S. Pat. No.4,354,424, issued Oct. 19, 1982, to Sven Nordlund, which is herebyincorporated herein by reference. In that actuator, each actuator pistonis provided with a rack having teeth thereon to engage correspondingteeth of an operating element. The rack includes a recess for receivinga first spring that produces a return force on the piston. The recessextends substantially into the rack of the piston. A second shorterspring is provided within a central portion of each actuator piston.Thus, one spring in each piston is offset from the center and is longerthan the other spring. The offset, longer spring provides a solution toa basic problem of compact spring return actuators. Prior to thisinvention, such actuators did not consistently have sufficient springforce to completely close the valve.

[0005] Many valves have requirements for drift adjustments that adjustthe valve position to an exactly open position and/or an exactly closedposition. For these cases, if the valve is not adjusted correctly, theflow path through the valve may not be completely open or accuratelyclosed due to an offset in the valve control element. If the flow pathis not accurately controlled, then the system efficiency may be reduced,failures may occur, and maintenance costs may increase. Thus, it isoften desirable to have a drift adjustment, or end stop adjustment, foradjusting the valve element for a more precise desired open and closedposition. A dual end stop adjustment in the actuator, which is known inthe prior art, permits adjustment of the open and closed position forthe valve by adjusting the extent of movement of the valve actuatorcontrol element. For a rotational valve actuator element, it is knownthat a dual end stop adjustment has been used to provide two rotationalstop positions for the rotational valve element.

[0006] The dual end stop adjustment may be used for many thousands ofvalve openings and valve closings over the lifetime of operation. Priorart end stop adjustments have a tendency change in drift or stopadjustment over time due to many openings and closings to therebypossibly cause deleterious operation of the valve system, significantlyincrease maintenance costs, and decrease overall system efficiency.

[0007] Prior art pneumatic actuators provide that the dual stopadjustment is sealed within the pressure zone of the actuator housing.Thus, the pressurized air, fluid, gas, and the like, used to activatethe valve is present at the stop adjustment mechanism. The inventor ofthe present invention considers this construction to be faulty and maylead to failures and inaccuracies in the stop adjustment. One of theproblems is that the pressurized housing is typically limited in sizeavailable for actuator mounting so that for a desired piston size, thethickness of the housing is also accordingly limited. The adjustmentbolts must therefore extend through the relatively thin wall of thehousing so as to be substantially unsupported along their length. Due tothis lack of support of the bolts and the relatively thin actuator wall,there is a tendency for bending and warping in prior art actuatorseither in the bolts or the actuator wall. Thus, the thousands ofopenings and closings of the valve may well lead to an unstable oreffectively non-operational drift adjustment thereby potentially causingvalve and/or valve system malfunctions.

[0008] The inventor has discovered other problems with existing dualstop adjustments for pneumatic actuators. One such problem concerns endstop bolts for engaging a stop surface wherein the flat head of the endstop bolt is subject to deformation, high spots, and the like which mayresult in an unstable drift adjustment. Another problem discovered bythe inventor relates to the mounting or adaptor plate used to secure theactuator to various types of valves which plates thereby adapt theactuator to the particular type of valve. Prior art mounting plates aresupported and positioned by bolts that are subject to offsets, bending,and warping which leads to inaccuracies in the dual end stop adjustmentsas well as the connection to the valve which may require high accuracyto standards, such as for instance, ISO standards. Another discoveredproblem relates to the machining cost of drilling numerous holes in themounting plates for support bolts. Depending on the location of thebolts, this can result in additional machining operations so that,according to the inventor, it would be desirable to achieve additionalreliability and accuracy with a reduced number of mounting bolt holes.Yet another discovered problem relates to bending and offsets of therotary drive shaft element due to torque applied to the rotary driveshaft element by the stop adjustment. Yet other discovered problemsrelate to stress in the mechanical supports for the dual end stopadjustment.

[0009] Consequently, there remains a need for a more reliable,consistent, and stable dual end stop adjustment that solves theabove-listed unaddressed problems and other problems of prior artpneumatic actuator dual end stop adjustment mechanisms. Those skilled inthe art have long sought and will appreciate the present invention whichprovides solutions to these and other problems.

SUMMARY OF THE INVENTION

[0010] The present invention was designed to provide more accurate andreliable operation of a pneumatic actuator to thereby more accuratelycontrol valve openings and closings over a lifetime of operation and toavoid deleterious changes that may greatly increase maintenance costsand reduce efficiency of a system of valves.

[0011] Therefore, it is an object of the present invention to provide animproved pneumatic actuator.

[0012] Another object of the present invention is to provide an improveddual end stop adjustment for a pneumatic actuator.

[0013] Yet another object of the present invention is to provide a dualend stop adjustment that does not vary in adjustment even after many,many, thousands of openings and closings of the valve.

[0014] These and other objects, features, and advantages of the presentinvention will 15 become apparent from the drawings, the descriptionsgiven herein, and the appended claims.

[0015] Therefore, the present invention may provide for a dual end stopfor a pneumatic actuator wherein the pneumatic actuator comprises anactuator housing which has a zone for pressure containment. A rotarydrive element is mounted for rotation within the actuator housing. Theapparatus comprises elements such as a stop element mounted to therotary drive element for rotation therewith. The stop element has afirst stop surface and a second stop surface. The stop element maypreferably be positioned outside of the zone for pressure containment. Afirst stop member is utilized for engaging the first stop surface. Thefirst stop member, in a preferred embodiment, may be mounted outside ofthe zone for pressure containment. A second stop member is also utilizedfor engaging the second stop surface and the second stop member may alsopreferably be mounted outside of the zone for pressure containment.

[0016] In a preferred embodiment, a first bearing is mounted on therotary drive element on a first side of the stop element. A secondbearing is mounted on a second side of the stop member opposite to thefirst side. In a presently preferred embodiment, the first bearing ismounted in the actuator housing adjacent a stop assembly housing and thesecond bearing is mounted in the stop assembly housing.

[0017] The stop assembly housing may preferably be provided defining anaperture therein. The stop assembly housing may preferably be mounted tothe actuator housing and the stop element may be positioned within thestop assembly housing. In a preferred embodiment, a first threadedportion for the first and/or second stop member engages and extends intoa receptacle such that more than eighty percent of the first threadedportion extending into the receptacle may be threadably engaged so as tobe supported within the receptacle.

[0018] In another aspect of the invention, a rounded, convex, ortapering end of the first and/or second stop member is engagable withthe first stop surface so as to provide a defined point contacttherewith.

[0019] The present invention also comprises a method forassembling/construction and may comprise steps such as providing therotary drive element with a first stop surface and a second stop surfacesuch that the first stop surface and the second stop surface arepreferably positioned outside of the zone for pressure containment.Other steps may preferably include providing a first stop member forengaging the first stop surface to stop the rotary drive element in afirst rotational position wherein the first stop member may be moveablerelative to the stop surface for adjusting the first rotationalposition. Another step comprises providing a second stop member forengaging the second stop surface to stop the rotary drive element in asecond rotational position wherein the second stop member may bemoveable relative to the stop surface for adjusting the secondrotational position.

[0020] Additional steps may include one or more of the following:mounting the first stop member and the second stop member within a stopassembly housing, providing an aperture within the stop assemblyhousing, providing a first radiuused section as part of the apertureadjacent the first stop member, providing a rounded end surface for thefirst stop member such that the rounded end surface is engagable withthe first stop surface, and/or providing support for the first stopmember such that the stop member is threadably supported at a positionclosely adjacent the rounded end.

[0021] In another preferred embodiment, a stop assembly housing may besized to fit into a recess in the actuator housing. The stop assemblyhousing defines an aperture therein. The first stop member may bemounted within the stop assembly housing such that the first stop memberis positionally adjustable and/or the second stop member may also bemounted within the stop assembly housing such that the second stopmember is positionally adjustable.

[0022] The stop assembly housing is preferably machined for accuracy toa desired size to thereby mate to the recess and the recess in theactuator housing is also preferably machined to a size for receiving thestop assembly housing such that lateral movement of the stop assemblyhousing within the recess is prevented. In a presently preferredembodiment, the stop assembly housing and the recess are machined to atolerance of less than or equal to one-one thousandth of an inch for atight fit of the stop assembly housing within the recess.

[0023] In a preferred embodiment, an outer bearing for the rotary driveelement is mounted within the stop assembly housing such that thebearing may be on an opposite side of the stop element from the actuatorhousing. An inner bearing may be provided for the rotary drive elementmounted within the actuator housing adjacent the stop assembly housing.

[0024] A first relief groove may preferably be defined in the stopassembly housing adjacent the first convex head and/or a second reliefgroove may preferably be defined in the stop assembly housing adjacentthe second convex head.

[0025] This aspect of the method for making and/or construction and/orassembly includes machining a receptacle in the actuator housing andmachining sides of a stop assembly housing that is insertable into thereceptacle. The steps of machining provide a tolerance between thereceptacle and the stop assembly housing such that the stop assemblyhousing is prevented from lateral movement.

[0026] For relieving stress in the stop assembly housing, a method ofthe invention may include steps such as providing an aperture within thestop assembly housing for receiving the rotary drive, providing a firstgroove along the aperture, and providing a second groove along theaperture. The first stop adjustment member has a first end for engagingthe first stop surface and the second stop adjustment member has asecond end for engaging a second stop surface. Thus, more specificallythe method may include steps such as providing the first groove adjacentthe first end, and providing the second groove adjacent the second end.

[0027] The first end stop may preferably have a first tapering end whichtapers to a first end point and the first tapering end surface may beengagable with the first stop surface for point contact to thereby stopthe rotary drive element in a first rotational position. Likewise asecond stop member may have a second tapering end which tapers to asecond end point. The second tapering end surface may be engagable withthe second stop surface for point contact to thereby stop the rotarydrive element in a second rotational position.

[0028] The present invention preferably utilizes bearings on either sideof the stop element to prevent bending of the shaft due to forcesapplied to the stop element. Thus, another method of the presentinvention may comprise steps such as installing a first bearing for therotary drive element for supporting a first end of the rotary driveelement, installing an outer bearing for the rotary drive element on anopposite side of the rotary drive element from the first end such thatthe outer bearing is positioned adjacent the stop element, andinstalling an inner bearing for the rotary drive element adjacent thestop element on an opposite side of the stop element with respect to theouter bearing.

[0029] In a preferred embodiment, the first and second stop members aresupported along its length. Thus, the rotary actuator may define a firstthreaded elongate aperture for receiving the first elongate stop member.The first threaded aperture has a first outer opening for receiving thefirst elongate stop member. The first threaded elongate aperture has alength of threaded surface such that at least eighty percent of aportion of the first elongate member which extends from the first outeropening to the first end is threadably supported by the length ofthreaded surface. Moreover, the second elongate stop member may bethreaded so as to be moveable along an axis thereof for adjustablyengaging the second stop surface. The second elongate stop member has asecond end for engaging the second stop surface and the rotary actuatormay define a second threaded elongate aperture for receiving the secondelongate stop member. The second threaded aperture has a second outeropening for receiving the second elongate stop member. The secondthreaded elongate aperture has a length of threaded surface such that atleast eighty percent of a portion of the second elongate member whichextends from the second outer opening to the second end is threadablysupported by the length of threaded surface.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 is an elevational view, partially in section, of a stopassembly housing or adaptor plate in accord with the present inventionshown in a first rotational stop;

[0031]FIG. 2 is an elevational view, partially in section, of the stopassembly housing or adaptor plate of FIG. 1 in a second rotational stopposition;

[0032]FIG. 3 is an elevational view of a drive shaft mounted on a stopassembly housing in accord with the present invention;

[0033]FIG. 4 is an elevational view, partially in cross-section, alongsectional view lines 4-4 of the actuator shown in FIG. 5;

[0034]FIG. 5 is an elevational view of an actuator in accord with thepresent invention showing a stop assembly housing mounted to theactuator housing;

[0035]FIG. 6 is an elevational view, of an actuator with a drive shaftextending therethrough; and

[0036]FIG. 7 is an elevational view, of an actuator with apertures inthe stop assembly housing for adjustment of the stop positions.

[0037] While the present invention will be described in connection withpresently preferred embodiments, it will be understood that it is notintended to limit the invention to those embodiments. On the contrary,it is intended to cover all alternatives, modifications, and equivalentsincluded within the spirit of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Referring now to the drawings, and more particularly to FIG. 1,FIG. 2, and FIG. 8, there is shown a dual end stop 10 in accord with thepresent invention. Dual end stop 10 includes adaptor plate or stopassembly housing 12 which preferably is used to house the various dualend stop components. Stop assembly housing 12 also acts as an adaptorplate to provide a connection or mounting between actuator housing 14,shown in FIG. 4, FIG. 5, FIG. 6, and FIG. 7, and the various types ofvalves (not shown) which actuator 16 may be mounted to.

[0039] It is well known that actuator pistons (not shown) withinactuator housing 14 may be used to activate rotary drive element 18, asshown in FIG. 3 and FIG. 4, to rotate in one direction, such as for aquarter turn, and then in the other direction by the same amount tothereby effect opening and closing of the valve. Mounted to ormonolithic with rotary drive element 18 is cam member 20 which acts as astop element affixed to rotary drive element 18. Other shapes andconfigurations of a stop element such as cam member 20 could also beused. Essentially, a stop element or stop element assembly for dual endstop 10 should comprise at least two stop surfaces, such as first stopsurface 22 and second stop surface 23. Rotary drive element 18 and cam20 then may rotate between a first rotational position as shown in FIG.1, and a second rotational position as shown in FIG. 2. First and secondrotational positions of cam 20 correspond with an open/closed positionof the valve. For instance, the position of FIG. 1 may correspond to anopen valve and the position of FIG. 2 may correspond to a closed valve.

[0040] Dual end stop 10 may be used to accurately set the open andclosed position of the valve. For instance, in one embodiment a firststop member such as stop adjustment bolt 24 and a second stop membersuch as adjustment bolt 26 may be adjusted by about plus and minus twoand one-half degrees thereby providing a range of travel for a rotarydrive of a quarter-turn actuator, such as rotary drive 18, and thecorresponding valve drive shaft, of a range of movement between abouteighty degrees and one hundred degrees. Depending on the actuator designand valve operational requirements, a somewhat greater range ofadjustment for each stop member could be provided if desired, forinstance, about plus and minus five degrees. For convenience ofoperation, stop adjustment bolts 24 and 26 are threaded bolts althoughother adjustable members could be used that may include gears, ratchets,and the like that may provide the sufficiently fine adjustments requiredto set the stops. In a presently preferred embodiment, lock nuts 28 and30 are used to lock stop adjustment bolts in position to prevent furtherrotation once the desired stop settings are made. In another embodimentof the invention as shown in FIG. 8, adjustment bolts 24A and 26A areprovided in a manner such that the adjustments are tamper resistant.Adjustment bolts 24A and 26A are not immediately available foradjustment thereby reducing the likelihood that inadvertent adjustmentmight be made by personnel. In this case, in line lock bolts 27 and 29are used to lock the position of adjustment bolts 24A and 26A,respectively. Lock bolts 27 and 29 cannot be used to make adjustments.Preferably, lock bolts 27 and 29 extend only slightly, if at all, fromstop assembly housing 12 to further discourage unneeded adjustments.

[0041] A preferred embodiment of the present invention utilizes severaldifferent special features to prevent any deformation of stop adjustmentbolts 24 and 26 and/or their mounting within stop assembly housing 12.Stop adjustment bolts 24 and 26 are preferably manufactured from hightensile steel.

[0042] Preferably stop adjustment bolts 24 and 26 and the correspondingapertures in which they are inserted, such as threaded apertures 32 and34, are designed for full thread engagement and minimum overhang of stopadjustment bolts 24 and 26 with respect to threaded apertures 32 and 34.For those prior art actuators which may use a rotating stop member, suchas cam 20, full thread engagement is not provided. The prior artadjustment bolts extend through the pressurized zone for engaging thestop surfaces and are supported by the actuator housing which is oftenrequired to be compact for suitable mounting to the valve. Thus, thereis much less support for rotary stop members. On the other hand, thepresent invention preferably utilizes a separate stop assembly housingpreferably mounted outside of the pressurized zone wherein the stopassembly housing preferably doubles as the adaptor plate to provide acompact design. Therefore, adjustment bolts 24 and 26 as well asthreaded apertures 32 and 34 can preferably be designed for a minimumoverhang. As a general matter, the length of each adjustment bolt 24 and26, which extends from initial openings 36 and 38 at side wall 40 intostop adjustment housing 12, are threadably engaged for about 95% of thislength. Preferably at least 80% of this inserted length of eachadjustment bolt 24 and 26 is threadably engaged within threadedapertures 32 and 34. This additional support as compared to prior artdesigns eliminates any possible deformation or warping of either theadjustment bolts or their associated support structure to therebyprovide a more stable dual stop setting adjustment. Thus, the featuresproviding a separate stop assembly housing and of positioning the stopadjustment bolts outside of the pressurized zone within actuator housing14 for a pneumatic actuator, as further discussed in more detailhereinafter, has significant long term benefits related to more stablestop setting adjustments.

[0043] Another preferred feature of the present invention is spherical,convex, rounded, and/or tapered bolt heads or bolt ends 36 and 38 foreach respective adjustment bolt 24 and 26. This structure is selected toproduce a defined contact point between first and second stop surfaces22 and 23 and the corresponding stop adjustment bolts 24 and 26. Byproviding a defined and centralized point contact, load distribution ismore uniform and less contact stress occurs on the mating faces. Thisdesign avoids the problems of prior art flat head bolts where there is apossibility of a random point contact associated with flat head boltsthat may result in a random contact face deformation leading to changingstop adjustment settings as well as random load distribution. Varioustapering designs for bolt ends 36 and 38 could be used although aspherical or convex profile is presently preferred.

[0044] Relief grooves 37 and 39 are provided adjacent bolt ends 36 and38, respectively, to thereby reduce stress in plate or stop assemblyhousing 12. The large blend radius of relief grooves 37 and 39 avoidsstress concentrations at the loaded bolt, the adjacent restraining boltholes 61 and 63, and the edge of stop bolt apertures 24 and 34. This inturn avoids the possibility of fatigue cracks propagating and ensuresthe present design has a superior fatigue life. In one finite analysistest, this design suggests the possibility of more than fifty millioncycles of repeated loadings without failure due to fatigue.

[0045]FIG. 3, FIG. 4, and FIG. 5 show the structural relationshipbetween rotary shaft 18, actuator housing 14, and stop assembly housing12. Referring to FIG. 3, a preferred rotary actuator shaft 18 is shownwhich may be rotated by gear teeth 42 and corresponding gear teeth onthe pistons and/or piston shaft (not shown). In a preferred embodiment,rotary actuator shaft 18 is supported by three bearings including topbearing 44 which may preferably be a split bearing for supportingactuator shaft 18 on one side of actuator housing 14. Actuator shaft 18extends through pressurized zone 46 of actuator housing 14 and may, asshown in FIG. 4, extend through both sides of actuator housing 14.Actuator shaft 18 is sealed adjacent bearing 44 by seal 48, which maypreferably be an O-ring or elastomeric seal. Retaining clip 50 andcorresponding rubbing ring 52 may be used to secure the axial positionof actuator shaft 18 with respect to actuator housing 14 whilepermitting rotation of actuator shaft 18.

[0046] It will be understood that such terms as “up,” “down,”“vertical,” and the like, are made with reference to the drawings and/orthe earth and that the devices may not be arranged in such positions atall times depending on variations in operation, transportation,mounting, and the like. As well, the drawings are intended to describethe concepts of the invention so that the presently preferredembodiments of the invention will be plainly disclosed to one of skillin the art but are not intended to be manufacturing level drawings orrenditions of final products and may include simplified conceptual viewsas desired for easier and quicker understanding or explanation of theinvention. As well, the relative size of the components may be greatlydifferent from that shown.

[0047] Actuator shaft 18 is also supported by lower bearing 54 on theopposite side of actuator housing 14 from bearing 44. Lower seal 56,which may preferably be an elastomeric or O-ring seal, seals aroundactuator shaft 18 adjacent to bearing 44. In a preferred embodiment,lower bearing 54 is provided within actuator housing 14 adjacent to stopassembly housing 12 and directly adjacent to one side of cam 20. Anotherbearing 58 is preferably provided within stop assembly housing 12 on theopposite side of cam 20 from lower bearing 54. The use of bearing 54 andbearing 58 on either side of cam 20 ensures that no deflection ofactuator shaft 18 will occur even under maximum applied loads. Thus,forces applied to cam 20 by stop adjustment members 24 and 26 againstcorresponding stop surfaces 22 and 23 will not cause deflection ofactuator shaft 18.

[0048] It will also be seen from FIG. 4 that stop assembly housing 12 ispreferably outside of pressure zone 46 which is sealed by seal 56. Thus,stop assembly housing 12 and the related components including stopadjustment members 24 and 26 as well as cam 20 with associated stopsurfaces 22 and 23 are all preferably positioned outside of pressurizedzone 46 contained within actuator housing 46. For safety and hygenicreasons, the stop surfaces and stop members are also preferably not opento ambience so fingers cannot be inserted therein and debris isprevented from reaching the stop surfaces and stop members.

[0049] In a preferred embodiment, stop assembly housing 12 is designedto be securely supported within recess 58 in actuator housing 14. Thefit between recess 58 and stop assembly housing 12 is preferably a verytight fit with tolerances in the range of about one-one thousandth of aninch. By providing a tight fit between stop assembly housing 12 andrecess 58 in actuator housing 14, the connection between thesecomponents is not only very accurate but also very strong and resiststorque, lateral movement, and other operating forces/stresses. In fact,in a preferred embodiment only two bolts such as bolts 60 and 62 arerequired because the only function of the bolts is to hold stop assemblyhousing 12 within recess 58. The position of stop housing 12 is alreadyfixed. Preferably both recess 58 and sides 40, 64, 66, and 68 of stopassembly housing 12 are milled rather than cast or molded to achieve thedesired accuracy of fit. In this manner, the adaptor plate, with orwithout the stop assembly, can be attached to the actuator housing for amore precise fit that can be made to conform with various standards suchas ISO standards that are used internationally for connecting actuatorsto valves such that the actuator and valve shafts align precisely. Dueto the costs of machining, the ability to use only two bolts to securestop assembly housing 12 to actuator housing 14 may result in reducedmachining costs, depending on the number and spacing of other holes,such as valve mounting holes 72, 74, 76, and 78 as well as alignmentring 80. The valve mounting configuration on stop assembly housing 12can be made to suit for CEN, ISO, or customer valve mountingconfiguration requirements. Shaft insert 82 will also suit standardssuch as ISO or customer valve requirements. The availability of threekey slots 84, 86, and 88 rather than just the two, in this case slots 84and 88, allows ninety degree rotation of shaft insert 82 as desired forproper mating to the valve.

[0050]FIG. 6 and FIG. 7 show external views of actuator 16 includingrelative location of shaft 18, with valve position indicator 90 on oneside of actuator housing 14, and an adaptor plate which also preferablycomprises stop assembly housing 12 on the opposite side thereof.

[0051] It will be seen that various changes and alternatives may be usedthat are contained within the spirit of the invention. For instance, themounting of the adaptor plate may be used whether or not the adaptorplate is also used as stop assembly housing 12 as is the presentlypreferred embodiment of the invention.

[0052] The foregoing disclosure and description of the invention isillustrative and explanatory thereof, and it will be appreciated bythose skilled in the art, that various changes in the size, shape andmaterials, the use of mechanical equivalents, as well as in the detailsof the illustrated construction or combinations of features of thevarious elements may be made without departing from the spirit of theinvention.

What is claimed is:
 1. A dual end stop for a pneumatic actuator, saidpneumatic actuator comprising an actuator housing, said actuator housinghaving a zone for pressure containment, a rotary drive element mountedfor rotation within said actuator housing, said dual end stopcomprising: a first stop surface and a second stop surface mounted forstopping said rotary drive element in a corresponding first rotationalposition and a second rotational position; a first stop member forengaging said first stop surface, said first stop member being mountedoutside of said zone for pressure containment; and a second stop memberfor engaging said second stop surface, said second stop member beingmounted outside of said zone for pressure containment.
 2. The dual endstop of claim 1, further comprising: a stop assembly housing defining anaperture therein, said stop assembly housing being mounted to saidactuator housing, a stop element being positioned within said stopassembly housing and defining thereon said first stop surface and saidsecond stop surface.
 3. The dual end stop of claim 2, furthercomprising: a first bearing for said rotary drive element mountedadjacent a first side of said stop element, and a second bearing forsaid rotary drive mounted adjacent a second side of said stop memberopposite to said first side.
 4. The dual end stop of claim 2, wherein athird bearing for said rotary drive element is mounted on an oppositeside of said rotary drive element and axially spaced from said firstbearing and said second bearing.
 5. The dual end stop of claim 1,further comprising a first threaded portion for said first stop memberthreadably engaged with a threaded receptacle, at least eighty percentof said first threaded portion threadably engaged said threadedreceptacle so as to be supported within said receptacle.
 6. The dual endstop of claim 1, further comprising a rounded end for said first stopmember, said rounded end engagable with said first stop surface.
 7. Amethod for an adjustable dual end stop for use with a pneumaticactuator, an actuator housing for said pneumatic actuator, said actuatorhousing having a zone for pressure containment, a rotary drive elementrotatably mounted within said actuator housing, said dual end stopcomprising providing said rotary drive element with a first stop surfaceand a second stop surface such that said first stop surface and saidsecond stop surface are positioned outside of said zone for pressurecontainment; providing a first stop member for engaging said first stopsurface to stop said rotary drive element in a first rotationalposition, said first stop member being moveable relative to said stopsurface for adjusting said first rotational position; and providing asecond stop member for engaging said second stop surface to stop saidrotary drive element in a second rotational position, said second stopmember being moveable relative to said stop surface for adjusting saidsecond rotational position.
 8. The method of claim 7, furthercomprising: mounting said first stop member and said second stop memberwithin a stop assembly housing.
 9. The method of claim 8, furthercomprising: providing an aperture within said stop assembly housing,providing a first radiuused section as part of said aperture adjacentsaid first stop member.
 10. The method claim 7, further comprising:providing a rounded end surface for said first stop member such thatsaid rounded end surface is engagable with said first stop surface. 11.The method of claim 10, further comprising: providing support for saidfirst stop member such that said stop member is threadably supported ata position closely adjacent said rounded end.
 12. A dual end stopadjustment for a rotary actuator, comprising: an actuator housing forsaid pneumatic actuator, said actuator housing having a zone forpressure containment, said actuator housing having a recess, a rotarydrive element rotatably mounted within said actuator housing; a stopassembly housing sized to fit into said recess, said stop assemblyhousing defining an aperture therein; a stop element on said rotarydrive element for rotation therewith, said stop element having a firststop surface and a second stop surface, said stop element beingpositioned within said aperture; a first stop member for engaging saidfirst stop, said first stop member being mounted within said stopassembly housing such that said first stop member is positionallyadjustable; and a second stop member for engaging said second stopsurface, said second stop member being mounted within said stop assemblyhousing such that said second stop member is positionally adjustable.13. The dual end stop adjustment of claim 12, wherein said stop assemblyhousing is machined to a desired size to thereby mate to said recess andsaid recess is machined to a size for receiving said stop assemblyhousing such that lateral movement of said stop assembly housing withinsaid recess is prevented.
 14. The dual end stop adjustment of claim 13,wherein said stop assembly housing and said recess are machined to atolerance of less than or equal to one-one thousandth of an inch for atight fit of said stop assembly housing within said recess.
 15. The dualend stop adjustment of claim 12, wherein: said stop assembly housing isheld in position with respect to said housing with no more than twothreaded connectors.
 16. The dual end stop adjustment of claim 12,further comprising: an outer bearing for said rotary drive elementmounted within said stop assembly housing, said bearing being on anopposite side of said stop element from said actuator housing.
 17. Thedual end stop adjustment of claim 16, further comprising: an innerbearing for said rotary drive element mounted within said actuatorhousing adjacent said stop assembly housing.
 18. The dual end stop ofclaim 12, further comprising: a first convex head for said first stopmember, said first convex head being engageable with said first stopsurface.
 19. The dual end stop of claim 18, further comprising: a firstrelief groove defined in said stop assembly housing adjacent said firstconvex head.
 20. A method for a dual end stop adjustment for a rotaryactuator, said rotary actuator having an actuator housing, said rotaryactuator having a rotary shaft rotatably mounted within said actuatorhousing, said method comprising: machining a receptacle in the actuatorhousing; machining sides of a stop assembly housing that is insertableinto said receptacle, said steps of machining providing a tolerancebetween said receptacle and said stop assembly housing such that saidstop assembly housing is prevented from lateral movement; and providingan aperture within said stop assembly housing for receiving a portion ofsaid rotary shaft.
 21. The method of claim 20, further comprising:mounting a first stop member within said stop assembly housing, mountinga second stop member within said stop assembly housing, and providing afirst stop surface and a second stop surface on said rotary shaft suchthat said first stop member is engageable with said first stop surfaceand said second stop surface is engageable with said second stopsurface.
 22. The method of claim 21, further comprising: providing acurved surface on said first stop member, said curved surface of saidfirst stop member being engageable with said first stop surface.
 23. Themethod of claim 21, further comprising: providing an engagement surfaceon said first stop member for engaging said first stop surface, andproviding a groove in said stop assembly housing adjacent saidengagement surface of said first stop member.
 24. The method of claim20, further comprising: providing an outer bearing for said rotary shaftwithin said stop assembly housing.
 25. The method of claim 20, furthercomprising: providing an inner bearing in said actuator housing adjacentto said stop assembly housing.
 26. A dual end stop for a pneumaticactuator, an actuator housing for said pneumatic actuator, said actuatorhousing having a zone for pressure containment, a rotary drive elementrotatably mounted within said actuator housing, said dual end stopcomprising: a stop assembly housing mountable to said housing, said stopassembly housing having an aperture therein for receiving a portion ofsaid rotary drive element; a stop element having a first stop surfaceand a second stop surface, said stop element being positioned withinsaid aperture; a first stop member having a first end stop, said firstend stop being engagable with said first stop surface; a second stopmember having a second end stop, said second end stop being engagablewith said second stop surface, said stop assembly housing furtherdefining a first stress relief groove adjacent said first end stop and asecond stress relief groove adjacent said second end stop.
 27. The dualend stop of claim 26, wherein said stop assembly housing is mountedoutside of said zone for pressure containment.
 28. The dual end stop ofclaim 26, wherein said first end stop has a curved surface, and saidsecond end stop has a curved surface.
 29. The dual end stop of claim 26,further comprising a bearing mounted within said stop assembly housingfor supporting said rotary drive element.
 30. A method for a dual endstop for a pneumatic actuator, said pneumatic actuator comprising anactuator housing, said actuator housing having a zone for pressurecontainment, a rotary drive element rotatably mounted within saidactuator housing, said method comprising: providing a stop assemblyhousing mountable to said actuator housing; providing an aperture withinsaid stop assembly housing for receiving said rotary drive; providing afirst groove along said aperture; and providing a second groove alongsaid aperture.
 31. The method of claim 30, further comprising: providinga first stop adjustment member with a first end for engaging a firststop surface, providing a second stop adjustment member with a secondend for engaging a second stop surface, providing said first grooveadjacent said first end, and providing said second groove adjacent saidsecond end.
 32. The method of claim 31, further comprising: providingthat said first end has a concave surface, and providing that saidsecond end has a concave surface.
 33. A dual end stop for a valveactuator, said valve actuator comprising an actuator housing, saidactuator housing having a zone for pressure containment, a rotary driveelement rotatably mounted within said actuator housing, a stop elementhaving a first stop surface and a second stop surface, said dual endstop comprising: a first stop member having a first end stop, said firstend stop having a first tapering end which tapers to first end point,said first tapering end surface being engagable with said first stopsurface for point contact to thereby stop said rotary drive element in afirst rotational position; and a second stop member having a second endstop, said second end stop having a second tapering end which tapers toa second end point, said second tapering end surface being engagablewith said second stop surface for point contact to thereby stop saidrotary drive element in a second rotational position.
 34. The dual endstop of claim 33, further comprising: said first tapering end having afirst convex surface, and said second tapering end having a secondconvex surface.
 35. The dual end stop of claim 33, further comprising: astop assembly housing mountable to said actuator housing, said firststop member and said second stop member being mountable within said stopassembly housing.
 36. The dual end stop of claim 34, further comprising:said stop assembly housing defining a first groove adjacent said firstend stop, and said stop assembly housing defining a second grooveadjacent said second end stop.
 37. The dual end stop of claim 33,wherein said first stop member and said second stop member are mountedoutside of said zone for pressure containment.
 38. A method for a dualend stop for a valve actuator, said valve actuator having an actuatorhousing, said actuator housing having a zone for pressure containment, arotary drive element rotatably mounted within said actuator housing, astop element having a first stop surface and a second stop surface, saiddual end stop comprising: providing a first stop member with a first endstop having a first tapering end surface, said first tapering endsurface being engagable with said first stop surface for stopping saidrotary drive element in a first rotational position; and providing asecond stop member with a second end stop having a second tapering endsurface, said second tapering end surface being engagable with saidsecond stop surface for stopping said rotary drive element in a secondrotational position.
 39. The method of claim 39, further comprising:forming a first tapering end surface with a convex profile, and formingsaid second tapering end surface with a convex profile.
 40. The methodof claim 38, further comprising: providing a stop assembly housingmountable to said actuator housing, and mounting said first stop memberand said second stop member within said stop assembly housing.
 41. Themethod of claim 39, further comprising: mounting a bearing within saidstop assembly housing for supporting said rotary drive element.
 42. Thedual end stop of claim 38, further comprising: mounting said first stopmember and said second stop member outside of said zone for pressurecontainment.
 43. A dual end stop adjustment for a rotary actuator,comprising: an actuator housing for said pneumatic actuator, saidactuator housing having a zone for pressure containment, a rotary driveelement rotatably mounted within said actuator housing; a stop elementon said rotary drive element for rotation therewith, said stop elementhaving a first stop surface and a second stop surface; a first stopmember for engaging said first stop surface; a second stop member forengaging said second stop surface; a first bearing for said rotary driveelement for supporting a first end of said rotary drive element; anouter bearing for said rotary drive element on an opposite side of saidrotary drive element from said first end, said outer bearing beingpositioned adjacent said stop element; and an inner bearing for saidrotary drive element adjacent said stop element on an opposite side ofsaid stop element with respect to said outer bearing.
 44. The dual endstop adjustment of claim 43, further comprising: a stop assemblyhousing, said first stop member and said second stop member beingmounted within said stop assembly housing.
 45. The dual end stopadjustment of claim 44, further comprising: said actuator housingdefining a recess, and stop assembly housing being positioned in saidrecess.
 46. The dual end stop adjustment of claim 43, furthercomprising: a stop assembly housing, said outer bearing being mounted insaid stop assembly housing.
 47. The dual end stop adjustment of claim43, further comprising: a first convex end for said first stop member,and a second convex end for said second stop member.
 48. A method for adual end stop adjustment for a rotary actuator, comprising: providing anactuator housing for said pneumatic actuator; providing a rotary driveelement rotatably mounted within said actuator housing; providing a stopelement on said rotary drive element for rotation therewith, said stopelement having a first stop surface and a second stop surface; providinga first stop member for engaging said first stop surface; providing asecond stop member for engaging said second stop surface; installing afirst bearing for said rotary drive element for supporting a first endof said rotary drive element; installing an outer bearing for saidrotary drive element on an opposite side of said rotary drive elementfrom said first end such that said outer bearing is positioned adjacentsaid stop element; and installing an inner bearing for said rotary driveelement adjacent said stop element on an opposite side of said stopelement with respect to said outer bearing.
 49. The method of claim 48,further comprising: providing a stop assembly housing, and mounting saidfirst stop member and said second stop member within said stop assemblyhousing.
 50. The method of claim 49, further comprising: forming arecess in said actuator housing, and mounting said stop assembly housingwithin said recess.
 51. The method of claim 48, further comprising:mounting a stop assembly housing to said actuator housing, and mountingsaid outer bearing being in said stop assembly housing.
 52. The methodof claim 43, further comprising: providing said first stop member with afirst convex end for engaging said first stop surface, and providingsaid second stop member with a second convex end for engaging saidsecond stop surface.
 53. A dual end stop adjustment for a rotaryactuator, comprising: an actuator housing for said pneumatic actuator, arotary drive element rotatably mounted within said actuator housing; astop element on said rotary drive element for rotation therewith, saidstop element having a first stop surface and a second stop surface; afirst elongate stop member, said first elongate stop member beingthreaded so as to be moveable along an axis thereof for adjustablyengaging said first stop surface, said first elongate stop member havinga first end for engaging said first stop surface; said rotary actuatordefining a first threaded elongate aperture for receiving said firstelongate stop member, said first threaded aperture having a first outeropening for receiving said first elongate stop member, said firstthreaded elongate aperture having a first length of threaded surfacesuch that at least eighty percent of said first elongate member betweensaid first outer opening of said first threaded aperture and said firstend is threadably supported by said first length of threaded surface; asecond elongate stop member, said second elongate stop member beingthreaded so as to be moveable along an axis thereof for adjustablyengaging said second stop surface, said second elongate stop memberhaving a second end for engaging said second stop surface; and saidrotary actuator defining a second threaded elongate aperture forreceiving said second elongate stop member, said second threadedaperture having a second outer opening for receiving said secondelongate stop member, said second threaded elongate aperture having asecond length of threaded surface such that at least eighty percent ofsaid second elongate member between said second outer opening of saidsecond threaded aperture and said second end is threadably supported bysaid second length of threaded surface.
 54. The dual end stop adjustmentof claim 53, further comprising: said actuator housing having a zone forpressure containment, said first elongate stop member being positionedoutside of said zone for pressure containment, and said second elongatestop member being positioned outside of said zone for pressurecontainment.
 55. The dual end stop adjustment of claim 53, furthercomprising: said first end having a first convex surface, and saidsecond end having a second convex surface.
 56. The dual end stopadjustment of claim 53, further comprising: a first external lock nutfor locking said first elongate stop member in position, and a secondexternal lock nut for locking said second elongate stop member inposition.
 57. The dual stop adjustment of claim 53, further comprising:a first lock screw mounted within said first threaded surface forlocking said first elongate stop member in position, and a second lockscrew mounted within said second threaded surface for locking saidsecond elongate stop member in position.
 58. The dual end stopadjustment of claim 53, further comprising: a stop assembly housingmounted to said actuator housing, said first threaded elongate aperturebeing formed in said stop assembly housing, and said second threadedelongate aperture being formed in said stop assembly housing.
 59. Amethod for a dual end stop adjustment for a rotary actuator, comprising:mounting a rotary drive shaft within said rotary actuator; providingsaid rotary drive shaft with a stop element for rotation therewith;providing said stop element to have a first stop surface and a secondstop surface; providing a first elongate stop member such that saidfirst elongate stop member is threaded so as to be moveable along anaxis thereof for adjustably engaging said first stop surface, said firstelongate stop member having a first end for engaging said first stopsurface; providing said rotary actuator with a first threaded elongateaperture for receiving said first elongate stop member, said firstthreaded aperture having a first outer opening, providing said firstthreaded elongate aperture with a length of threaded surface such thatat least eighty percent of a portion of said first elongate member whichextends from said first outer opening to said first end is threadablysupported by said length of threaded surface; providing a secondelongate stop member such that said second elongate stop member isthreaded so as to be moveable along an axis thereof for adjustablyengaging said second stop surface, said second elongate stop memberhaving a second end for engaging said second stop surface; and providingsaid rotary actuator with a second threaded elongate aperture forreceiving said second elongate stop member, said second threadedaperture having a second outer opening, providing said second threadedelongate aperture with a length of threaded surface such that at leasteighty percent of a portion of said second elongate member which extendsfrom said second outer opening to said second end is threadablysupported by said length of threaded surface.
 60. The method of claim59, further comprising: providing said actuator with an actuator housinghaving a zone for pressure containment, mounting said first elongatestop member outside of said zone for pressure containment, and mountingsaid second elongate stop member outside of said zone for pressurecontainment.
 61. The method of claim 59, further comprising: providingsaid first end with a first convex surface, and providing said secondend with a second convex surface.
 62. The method of claim 59, furthercomprising: providing a first external lock nut for locking said firstelongate stop member in position, and providing a second external locknut for locking said second elongate stop member in position.
 63. Themethod of claim 59, further comprising: mounting a stop assembly housingto said actuator housing, forming said first threaded elongate aperturein said stop assembly housing, and forming said second threaded elongateaperture in said stop assembly housing.
 64. A rotary valve actuator,comprising: an actuator housing, said actuator housing defining arecess; a rotary actuator shaft mounted for rotation within saidactuator housing; an adaptor plate mounted within said recess of saidactuator housing such that said adaptor plate fits tightly within saidrecess, said adaptor plate defining an aperture for receiving saidrotary actuator shaft.
 65. The rotary valve actuator of claim 64,wherein: said recess and said adaptor plate is machined to a closetolerance to thereby prevent lateral movement of said adaptor platewithin said recess.
 66. The rotary valve actuator of claim 64, furthercomprising: no more than two fasteners for securing said adaptor platewithin said recess.
 67. The rotary valve actuator of claim 64, furthercomprising: one or more stop elements mounted within said adaptor plate.68. An adaptor plate for a pneumatic actuator, said pneumatic actuatorcomprising an actuator housing with a pressurized zone, an actuatorshaft mounted within said pneumatic actuator, said adaptor platecomprising: first and second stop adjustment members mounted within saidadaptor plate, said adaptor plate defining an aperture for receivingsaid actuator shaft, first and second stop surfaces for engagement withsaid first and second stop adjustment members, respectfully, saidadaptor plate being mounted to said actuator housing outside of saidpressurized zone.
 69. A dual end stop adjustment for a rotary actuator,comprising: an actuator housing for said pneumatic actuator, a rotarydrive element rotatably mounted within said actuator housing; a stopelement on said rotary drive element for rotation therewith, said stopelement having a first stop surface and a second stop surface; a firstelongate stop member, said first elongate stop member being threaded soas to be moveable along an axis thereof for adjustably engaging saidfirst stop surface, said first elongate stop member having a first endfor engaging said first stop surface; said rotary actuator defining afirst threaded elongate aperture for receiving said first elongate stopmember; a first threaded lock screw mounted within said first threadedsurface for locking said first elongate stop member in position; asecond elongate stop member, said second elongate stop member beingthreaded so as to be moveable along an axis thereof for adjustablyengaging said second stop surface, said second elongate stop memberhaving a second end for engaging said second stop surface; and saidrotary actuator defining a second threaded elongate aperture forreceiving said second elongate stop member; and a second lock screwmounted within said second threaded surface for locking said secondelongate stop member in position.